Vulnerability assessment for the Gaza Strip, Palestine using DRASTIC

The main usefulness of groundwater vulnerability assessment maps is their ability to be an effective preliminary tool for planning, policy, and operational levels of decision-making. DRASTIC is one such assessment method. The DRASTIC index is made up of a calculated sum of products rating and weights for seven hydrogeological parameters that contribute to aquifer vulnerability. With the help of GIS, and based on the available data, maps of DRASTIC parameters were prepared for the Gaza Strip area in a case study. Each map was given a proper rate and a special weight factor developed. The final vulnerability map was obtained as a summation of the seven maps after multiplying each one with the appropriate weight. The vulnerability map was checked against the actual pollution potential in the area and nitrate concentration. The obtained vulnerability map is strongly correlated to known pollution values in the area.     

Assessment of groundwater vulnerability in the Río Artiguas basin, Nicaragua

The Río Artiguas basin in central Nicaragua shows a distinctive case of environmental deterioration due to anthropogenic activities. Heavy metals used in gold mining and other wastes are continuously released into the rivers, representing a threat to the water quality. This article aims to evaluate the groundwater intrinsic vulnerability in the Río Artiguas basin and to provide information for sustainable use of water resources. The DRASTIC and GOD methods were used to analyse the relative pollution potential within the basin. DRASTIC was modified to include the degree of influence that geological structures have on the vulnerability. Moderate vulnerability areas cover most of the basin along stream valleys and lowlands, increasing downstream in the basin. The resulting vulnerability maps show that the limited groundwater resources are susceptible to surface water pollution as high vulnerability areas converge along the river valleys.     

Validation of vulnerability mapping methods by field investigations and numerical modelling

Vulnerability maps illustrate the potential threat of contaminants to groundwater and can be considered as important tools for land-use planning and related legislation. For karst areas with characteristic preferential infiltration conditions, vulnerability maps are also excellent tools for source and resource protection. However, the resulting qualitative maps are often inconsistent and even contradictive and thus might lead to inconclusive vulnerability assessments. The results of a validation of vulnerability maps produced using four different methods, DRASTIC, GLA, PI and EPIK, are reported for a karst area in southwest Germany. By means of measured hydraulic and transport parameters of the geological sequence, numerical simulations were used based on a conceptual model for the area under study. The mean transit time through the unsaturated zone (resource protection) was used as the validation parameter. The study demonstrates that the highest level of accuracy is achieved with the GLA- and PI methods. Both DRASTIC and EPIK are not able to incorporate highly variable distributions and thickness of cover sediments and their protective properties in the respective mapping procedure. Thus, vulnerability maps produced with DRASTIC, EPIK, and related methods should be used with care when employed in vulnerability assessments for land use planning and related decision-making.

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Résumé  Les cartes de vulnérabilité illustrent la menace potentielle des contaminants envers les eaux souterraines, et peuvent être considérées comme des outils importants en matière d'aménagement foncier et de réglementation associée. Sur les domaines karstiques, caractérisés par des conditions d'infiltration préférentielle, ces cartes sont également d'excellents outils de protection des sources et des ressources. Cependant, les cartes qualitatives résultantes sont généralement incohérentes voire contradictoires, et peuvent par là-même mener à des évaluations de vulnérabilité peu concluantes. La présente étude expose les résultats de validation de cartes de vulnérabilité produites selon quatre méthodes différentes (DRASTIC, GLA, PI et EPIK), dans le cas d'un domaine karstique du sud-est de l'Allemagne. Par le biais des paramètres de transport et hydrauliques mesurés sur la séquence géologique, des simulations numériques basées sur un modèle conceptuel du secteur d'étude ont été utilisées. Les temps de transit moyens à travers la zone non saturée (protection de la ressource) ont été utilisés comme paramètres de validation. L'étude démontre que le niveau maximum de précision est obtenu par les méthodes GLA et PI. Dans la phase de cartographie, les méthodes EPIK et DRASTIC sont incapables d'intégrer une forte variabilité dans les distributions et les épaisseurs de sédiments de couverture, ainsi que dans leurs potentiels de protection. Aussi, les cartes de vulnérabilité produites par les méthodes DRASTIC et EPIK doivent être utilisées avec précaution dans le cadre des évaluations de vulnérabilité à but décisionnaire pour les aménagements fonciers.

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Resumen  Los mapas de vulnerabilidad ilustran la amenaza potencial de contaminantes para el agua subterránea y pueden ser considerados herramientas importantes para planeamiento del uso de la tierra y legislación relacionada. Para áreas cársticas con sus características condiciones de infiltración preferencial, los mapas de vulnerabilidad son también excelentes herramientas para protección de fuentes y recursos. Sin embargo, los mapas cualitativos resultantes son frecuentemente inconsistentes y hasta contradictorios y por lo tanto podrían conducir a evaluaciones de vulnerabilidad no concluyentes. Los resultados de una validación de mapas de vulnerabilidad producidos usando cuatro métodos diferentes, DRASTIC, GLA, PI y EPIK, son presentados aquí para un área cárstica en Alemania suroccidental. Se usaron simulaciones numéricas usando parámetros hidráulicos y de transporte medidos de la secuencia geológica y basándose en un modelo conceptual del área en estudio. El tiempo promedio de tránsito a través de la zona no saturada (protección del recurso) fue utilizado como el parámetro de validación. El estudio demuestra que el máximo nivel de precisión es alcanzado con los métodos GLA y PI. DRASTIC y EPIK no fueron capaces de incorporar distribuciones altamente variables ni espesor de sedimentos de cubierta y sus propiedades protectivas en el respectivo procedimiento de elaboración de mapas. Por lo tanto los mapas de vulnerabilidad producidos con DRASTIC, EPIK y métodos relacionados deberían ser usados con cuidado cuando se usen en evaluaciones de vulnerabilidad para planeamiento del uso de tierra y toma de decisiones relacionadas.

     

A methodological framework for rapidly assessing the impacts of climate risk on national-level food security through a vulnerability index

This article describes an experimental Hunger and Climate Vulnerability Index showing the relative vulnerability of food insecure populations to climate risks at country level, as a tool for better understanding risks to food security presented by climate change. Data from socioeconomic and environmental indicators were analysed, and the most relevant indicators were aggregated using a composite index to compare differential vulnerabilities. The paper shows the high correlation between hunger and climate risk, especially for the regions of the world most affected by food insecurity. The analysis goes beyond the impact of climate on crop yields and provides a multidimensional analysis of vulnerability, while demonstrating the critical role that adaptive capacity has in determining vulnerability. The paper also presents a method for analysing food security vulnerability to climate risks that is replicable at different scales to provide a robust planning tool for policy makers. This approach can also be used to monitor vulnerability, evaluate potential effectiveness of programmes, and/or examine plausible impacts of climate change by introducing scenarios into the vulnerability model.     

Rivers as municipal infrastructure: Demand for environmental services in informal settlements along an Indonesian river

In many developing world cities, where municipal infrastructure lags urban growth, lower-income communities may compensate by relying on local waterways to meet basic needs for water, sanitation, and recreational space. Access to these environmental services is possible because residents settle in floodplains, but thus entails elevated exposure to several water-related hazards, especially flooding. We examine this complex relationship in the neighborhoods of Bukit Duri and Kampung Melayu on the Ciliwung River in Jakarta, Indonesia. Based on a spatially referenced household survey, we analyze and map the patterns of use of six environmental services provided by the river: direct sanitary use, recreation, harvesting plants, groundwater use, solid waste disposal, and sewage disposal. Using spatial interpolation and regression methods, we identify the most probable areas where services are being used and analyze possible influences on this behavior. We find that proximity to the river significantly influences households’ behavior toward the river, as do infrastructure-related variables and neighborhing households’ behavior, while household demographic factors appear less significant. These results indicate that many households rely on multiple environmental services, and that residents most reliant on these services are also at greater risk of water-related hazards, service disruption (e.g., a decline in water quality), and potentially, eviction. This pattern of floodplain development is prevalent in many low-income countries, and a better understanding of how informal settlements rely on environmental services can be used to assess their vulnerabilities and inform more sustainable courses of development.     

Adapting towards climate change impacts: Strategies for small-scale fishermen in Malaysia

As with the global scenario, a number of climate change ‘symptoms’ are being detected in Malaysia. Local scholars have looked into the problems of rising temperature, rising sea level, extreme rainfall and extreme winds, which are causing coastal and mangrove erosion and degradation of marine resources. In turn, these issues are affecting the small-scale fishermen who rely heavily on weather stability to conduct their social and economic routines. This paper analyses six adaptation strategies, namely, reducing the risks associated with fishing routines, strengthening social relationships, managing fishermen's climate change knowledge, facilitating the community's learning of alternative skills, involving fishermen in climate change adaptation planning, and enhancing fishermen's access to credit. These suggestions are hoped to provide basis for concerned parties to develop adaptation strategies that are in line with small-scale fishermen's needs, abilities and interests.     

A new model (DRARCH) for assessing groundwater vulnerability to arsenic contamination at basin scale: a case study in Taiyuan basin,northern China

A modified DRASTIC model for groundwater vulnerability assessment (abbreviated as DRARCH model by combining the first letters of its six assessment indices) was proposed. It is essentially the specific application of DRASTIC model rather than a new model. Both natural hydrogeological conditions that prevent groundwater from contamination and important intrinsic hydrogeochemical properties of sediments in vadose zone that are related to the retardation of contaminants were considered as vulnerability indices. The DRARCH model consists of six indices: (1) Depth to the water table, (2) net Recharge, (3) Aquifer thickness, (4) Ratio of cumulative thickness of clay layers to total thickness of vadose zone, (5) Contaminant adsorption coefficient of sediment in vadose zone, and (6) Hydraulic conductivity of aquifer. The rating values and the weights of these vulnerability indices were obtained by contaminant transport simulation and factor analysis method respectively. Furthermore, the DRARCH model was applied to evaluate the groundwater vulnerability to arsenic contamination in Taiyuan basin, northern China, where groundwaters with high arsenic concentration occur in some localities. GIS-based mapping of groundwater vulnerability using this model indicates that the distribution of very high and high-vulnerability areas corresponds well to that of high-arsenic groundwaters. The DRARCH model is therefore reliable and useful for guiding groundwater environment management.     

全球气候变化下水资源脆弱性及其评估方法

气候变化对水资源的影响主要表现在两个方面:①对水资源供给能力的影响;②对水资源需求性的影响。气候变化下水资源脆弱性评估是水资源系统的综合评估,主要包括水资源供给与需求平衡的评估。我国水资源深受气候影响,表现在地区分布不均、洪涝灾害严重、供需矛盾突出等方面;此外,自气候变化引起关注以来,我国有关水资源脆弱性评估的研究甚少。对水资源脆弱性评估方法进行探讨,旨在为进一步探讨气候变化下我国水资源的脆弱性提供依据。     

GIS-based risk analysis of debris flow： an application in Sichuan, southwest China

Debris flow is a serious geologic hazard in China. It is estimated that nationally debris flows cause up to 2 billion RMB （250 million US$） in damages and 300-600 deaths and injuries annually. To mitigate debris flow hazards, it is necessary to map, model, and identify zones of debris flow hazards and vulnerability as to inform the local people about the potential risk with a geographic information system. This research presents a regional scale case study modeling debris flow risk （hazard and vulnerability） in Sichuan Province, Southwestern China. In this area, 3,290 debris flows have been identified and the spatial-temporal distribution and activity characteristics of them have been documented. Based on the available meteorological data, a Digital Elevation Model with the rate of 1：250,000 and a regional geological map, the 24-hr rainfall threshold （y） for debris flow occurrence is closely related （significant at 99% confidence level） to the index （x） defined using a geology factor （rock hardness： a） and a topographical factor （channel gradient： d） where y = 21 ＋ 10200 / x, in which x = 2.7 × e^a ＋ 1000 × d. The discipline is constructive in developing the rainfall threshold for debris flow activity in remote mountainous areas that lack data. For a given watershed, a four-level debris flow hazard map is developed by comparing the rainfall threshold to the design rainfall intensities with 50-, 20-, and 5-year average recurrence intervals, respectively. The degree of debris flow vulnerability is determined by the watershed socio-economic conditions. A four-class debris flow risk map, at the final phase of the research, is generated by combining debris flow hazards and vulnerability. With the debris flow risk assessment, the Sichuan Province is classified into the slight, moderate, severe and very severe regions, which accounts for 36%, 19%, 20% and 25% of total area respectively.